Apparatus and method for separating ferrous and non-ferrous metal particles suspended in a liquid

ABSTRACT

A method and apparatus for separating ferrous metal particles from non-ferrous metal particles suspended in a liquid, such as a coolant from a machining operation, in which mixed particle containing liquid is discharged across a horizontal, non-magnetic separating surface; the magnetic ferrous metal particles are captured by a magnetic force exerted by an array of parallel magnets disposed underneath the separating surface, the non-magnetic non-ferrous metal particles are washed by the liquid into a collecting flume from where they can be passed to a filtering station for removal from the liquid, and the captured ferrous metal particles are scraped from the separating surface and conveyed to a ferrous metal discharge by a scraper conveyor which moves transversely to the discharge direction of the liquid.

BACKGROUND OF THE INVENTION

Modern motor vehicles increasingly incorporate amounts of non-ferrousmetals. Aluminum, in particular, is finding increasing applicationbecause it combines high strength with low weight. Thus, manufacturingplants for engines, transmissions and other automotive components nowcommonly have to machine both ferrous metal and non-ferrous metal parts,thereby producing ferrous metal and non-ferrous metal chips.

Sound manufacturing practice calls for the recycling of waste metal. Therecycling of aluminum has particular economic significance in view ofthe substantial amount of energy which is consumed in the production ofaluminum.

Since substantially pure metals have much more economic value than mixedmetal, it is important to be able to segregate ferrous metal chips fromnon-ferrous metal chips. One approach for accomplishing this has been toprovide separate chip collecting and processing facilities for machinetools that produce ferrous metal parts and for those that producenon-ferrous metal parts. This, however, requires dual or duplicatecoolant/lubricant collecting systems and chip filtration and processingsystems. Such dual or duplicate systems both waste space and require anincreased investment in plant and machinery, with a consequent adverseeffect on manufacturing economics.

Attempts have also been made in the past to separate suspended ferrousmetal particles from non-ferrous metal particles by using differentialsettling methods based upon the fact that ferrous metal particles, dueto their generally higher density, will settle more rapidly than thelighter non-ferrous metal chips. Such methods, however, have not beeneffective to achieve the required degree of separation.

Another approach attempted in the prior art has involved collecting bothferrous metal and non-ferrous metal chips together, and then separatingthe ferrous metal chips from the non-ferrous metal chips, for example bymagnetic separators. Such attempts have been less successful thandesired because the magnetically collected ferrous metal chips tend tophysically trap non-ferrous metal chips so that the desired degree ofseparation is not achieved.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to provide a method foreffectively separating ferrous metal and non-ferrous metal particlesentrained in a liquid medium.

It is also an object of the invention to provide a method of separatingferrous metal and non-ferrous metal chips which can achieve a highdegree of separation in an economically efficient manner.

A further object of the invention is to provide an improved apparatusfor separating ferrous metal and non-ferrous metal particles entrainedin a liquid.

An additional object of the invention is to provide an apparatus forseparating ferrous metal and non-ferrous metal chips which achieves ahigh degree of separation with a simple and reliable construction.

In a first aspect of the invention, these and other objects are achievedby providing a method of separating ferrous metal chips from non-ferrousmetal chips suspended in a liquid, said method comprising discharging aliquid containing a mixture of suspended ferrous and non-ferrous metalparticles from a first side onto a horizontal separating surface ofnon-magnetic material; capturing and holding ferrous metal particles onsaid separating surface in a magnetic field exerted by an array ofmagnets arranged under said separating surface; washing non-ferrousmetal particles in said liquid across said separating surface;collecting said liquid containing non-ferrous metal particles at asecond side of said separating surface opposite said first side; andscraping the captured ferrous metal particles from said separatingsurface and conveying the ferrous metal particles to a collectingvessel.

According to a further aspect of the invention, the objects of theinvention are achieved by providing an apparatus for separating ferrousmetal chips from non-ferrous metal chips suspended in a liquid, saidapparatus comprising a horizontal separating surface of non-magneticmaterial; at least one liquid discharge arranged at a first side of saidseparating surface for discharging liquid containing a mixture ofsuspended ferrous and non-ferrous metal chips across said separatingsurface; a plurality of magnets arranged under said separating surfacefor capturing ferrous metal chips from said liquid; a collecting flumefor collecting liquid and non-ferrous metal chips disposed adjacent asecond side of said separating surface opposite said first side, and aconveyor for carrying away captured ferrous metal chips from saidseparating surface.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in further detail hereinafter withreference to an illustrative preferred embodiment depicted in theaccompanying drawings in which

FIG. 1 is a side elevational view of an apparatus for separating ferrousand non-ferrous metal chips according to the present invention;

FIG. 2 is a top plan view of the apparatus of FIG. 1; and

FIG. 3 is an end view of the apparatus.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

FIG. 1 shows a side elevational view of a preferred separating apparatusaccording to the present invention, generally designated by thereference numeral 1. The apparatus comprises a collecting tank or hopper3. A feed pipe 5, leading from a collecting station (not shown) forcoolant from one or more machining operations, leads to an inlet 11 inthe side of tank 3 to admit chip-containing coolant to the tank. Thebottom 13 of tank 3 is inclined and leads to an outlet 15, which in turnis connected to a discharge pipe 17. A pump 19 on discharge pipe 17driven, for example, by a motor 21 withdraws collected chip-containingcoolant from the tank 3 and pumps it through supply line 23 and riser 25to a distribution header 27. Header 27, in turn, is connected to aplurality of down lines 29 each terminating in a laterally directednozzle 31. In the illustrated embodiment eight down lines and nozzlesare shown, but it will be appreciated by persons of ordinary skill thata greater or lesser number of down lines and nozzles may be provided.Each down line 29 is provided with a regulating valve 33 which serves toregulate the discharge of chip-containing coolant from the respectivenozzle 31.

The nozzles 31 are oriented to discharge chip-containing coolant acrossa horizontal separating surface 35. The separating surface 35 should beformed of a non-magnetic material, such as stainless steel. Theseparating surface 35 transitions smoothly at one end into an upwardlyinclined discharge surface 37 which terminates at a discharge chute 39leading to a collecting bin 41.

Underneath separating surface 35 are arranged a plurality of permanentmagnets 43. Magnets 43 are preferably arranged in a parallel array sothat chip-containing coolant discharged across separating surface 35will successively traverse the magnetic fields of a plurality ofmagnets. The side of separating surface 35 opposite nozzles 31 isbounded by a collecting chamber or flume 55 having an inclined bottom 57leading to a coolant outlet 59. The collecting flume 55 is arranged suchthat liquid flowing over the edge 54 of separating surface 35 will becaptured and directed through outlet 59.

An endless chain conveyor 51 mounted on sheaves 46 on shafts 45 and 47,disposed at respective ends of separating surface 35 is arranged to dragscraper flights along separating surface 35 transversely to thedirection of liquid discharge thereover and up inclined dischargesurface 37. Like the separating surface 35, the scraper flights 53 arepreferably manufactured of a suitable non-magnetic material such asstainless steel. A motor 49 is provided to drive the conveyor system.

The apparatus operates according to the method of the invention asfollows:

Contaminated coolant containing suspended ferrous metal and non-ferrousmetal chips from machining operations is received through feed line 5and inlet 11 into tank 3. From the tank, the mixed chip containingcoolant is pumped by pump 19 through lines 17, 23 and 25 to distributionheader 27. From the header 27, the liquid flows through down lines 29and is discharged from nozzles 31 across separating surface 35. Themagnetic field established by magnets 43 captures ferrous metalparticles on separating surface 35. The continued flow of coolant liquidwashes non-ferrous metal chips across the separating surface 35 and overedge 54 into collecting chamber 55.

Ferrous metal chips captured by the force of magnets 43 are collected byscrapers 53 pulled by the endless conveyor 51 and drawn up dischargesurface 37, from which they pass through discharge chute 39 intocollecting vessel 41. The non-ferrous metal chip containing coolantliquid received by collecting chamber 55 is discharged through outlet 59to a suitable filtration apparatus (not shown) where the non-ferrousmetal chips can be separated from the liquid.

Valves 33 can be adjusted as needed to control the rate of liquiddischarge across surface 35 so that non-ferrous metal chips are reliablywashed out of the magnetically captured ferrous metal chips on thesurface. The optimum liquid discharge velocity will vary depending uponthe degree of contamination of the coolant liquid with ferrous metal andnon-ferrous metal chips, as well as the width of the separating surface.For separating surface widths on the order of 0.75 to 1 meter, goodresults have been obtained with discharge velocities in the range fromabout 2 to about 3 meters per second (approx. 7 to 10 feet per second).

The volume of liquid discharged over the separating surface willnecessarily vary depending on the size of the separating surface, thestrength of the magnets, and the degree of particle contamination in theliquid. The liquid discharge rate should be sufficiently low that theliquid depth does not exceed about 3 centimeters. It is preferred tomaintain the liquid depth not more than about 2 centimeters. The amountof liquid, however, should be sufficient to effectively wash non-ferrousmetal particles away from captured ferrous metal particles and thereforethe minimum liquid depth will ordinarily be at least as high as thedepth of the ferrous metal particle accumulations on the surface.

The pitch or spacing of scrapers 53 on endless conveyor 51 and the speedof the conveyor are adjusted to rapidly clear the captured ferrous metalchips from the separating surface, so that there is no buildup of largeaccumulations of ferrous metal chips in which the non-ferrous metalchips may be trapped. Good results have been achieved with a flightspacing of approximately 13 centimeters (5 inches) and a conveyor speedof about 2 to 5 meters per minute, preferably about 2.5 to 3 meters perminute.

Any desired type of magnet may be used in the apparatus of theinvention. It is preferred to use permanent magnets. Particularly goodresults have been obtained with ceramic magnets of sintered strontiumferrite. Such magnets are commercially available, for example from theBunting Magnetics Company of Cleveland, Ohio, USA or from the EriezMagnetic Co. of Erie, Pa., USA. Stainless steel cladding on the back andsides of the magnets may help both to enhance the durability of themagnets and also to channel the magnetic force toward the separatingsurface. The magnets must be of sufficient strength to capture and holdthe magnetic chips against the force of the moving liquid. Good resultshave been achieved with magnets which exert a magnetic induction in therange from about 1,500 to about 3,000 gauss. In tests of the invention,excellent separation has been achieved with an array of 8 approximately4 inch wide magnets having a magnetic induction of 2,200 gauss spacedapproximately 1 centimeter apart. The magnets should be arranged withthe north pole of one proximate the south pole of the adjacent magnet.

The nozzles may be simple pipe nipples of, for example, 2 inch pipe. Ifdesired, threaded connections may be provided so that the nozzles may beconveniently exchanged for nozzles of other sizes. If desired, thenozzles may have a non-circular configuration. For example, it may beadvantageous to provide nozzles with an oval outlet opening, with thelong axis of the oval arranged parallel to the separating surface toprovide a more rapid and even distribution of the chip-containing liquidover the separating surface.

The foregoing description and examples have been set forth merely toillustrate the invention and are not intended to be limiting. Sincemodifications of the described embodiments incorporating the spirit andsubstance of the invention may occur to persons skilled in the art, theinvention should be construed broadly to include everything within thescope of the appended claims and equivalents thereof.

1. An apparatus for separating ferrous metal chips from non-ferrousmetal chips suspended in a liquid, said apparatus comprising: ahorizontal separating surface of non-magnetic material; at least oneliquid discharge arranged at a first side of said separating surface fordischarging liquid containing a mixture of suspended ferrous andnon-ferrous metal chips across said separating surface; a plurality ofmagnets arranged under said separating surface for capturing ferrousmetal chips from said liquid; a collecting flume for collecting liquidand non-ferrous metal chips separately from said captured ferrous metalchips, said collecting flume disposed adjacent a second side of saidseparating surface opposite said first side; and a conveyor for carryingaway captured ferrous metal chips from said separating surface.
 2. Anapparatus according to claim 1, wherein said magnets are arrangedsuccessively in a discharge direction of said liquid discharge andparallel to one another.
 3. An apparatus according to claim 1, whereinsaid conveyor moves transversely to a discharge direction of said liquiddischarge.
 4. An apparatus according to claim 3, wherein said conveyorcomprises an endless chain carrying a succession of scraper flightswhich are drawn across said separator surface toward a ferrous chipdischarge.
 5. An apparatus according to claim 1, wherein said at leastone liquid discharge comprises a plurality of spaced liquid dischargenozzles arranged along said first side of said separating surface.
 6. Anapparatus according to claim 1, further comprising at least oneregulating valve for controlling liquid flow through said liquiddischarge.
 7. An apparatus according to claim 1, wherein said liquid onsaid separating surface is maintained at a depth of at most 3 cm.
 8. Anapparatus according to claim 7, wherein said liquid on said separatingsurface is maintained at a depth of at most 2 cm.
 9. An apparatusaccording to claim 1, wherein said separating surface is comprised ofstainless steel.
 10. An apparatus according to claim 1, wherein saidmagnets are sintered strontium ferrite ceramic magnets.
 11. An apparatusaccording to claim 10, wherein said magnets are stainless steel clad onall sides except the side adjacent said separating surface.
 12. Anapparatus according to claim 1, wherein said liquid is discharged at avelocity of from about 2 to about 3 meters per second.
 13. An apparatusaccording to claim 1, wherein said magnets exert a magnetic induction offrom 2000 to 2500 gauss through said separating surface.
 14. A method ofseparating ferrous metal particles from non-ferrous metal particlessuspended in a liquid, said method comprising: discharging a liquidcontaining a mixture of suspended ferrous and non-ferrous metalparticles at a first side of a horizontal separating surface ofnon-magnetic material; capturing and holding ferrous metal particles onsaid separating surface in a magnetic field exerted by an array ofmagnets arranged under said separating surface; collecting said liquidcontaining non-ferrous metal particles separately from said capturedferrous metal particles at a second side of said separating surfaceopposite said first side of said separating surface; and scraping thecaptured ferrous metal particles from said separating surface andconveying the ferrous metal particles to a collecting vessel.
 15. Amethod according to claim 14, wherein said magnets are arrangedsuccessively in a discharge direction of said liquid discharge andparallel to one another.
 16. An method according to claim 14, whereinsaid captured ferrous metal particles are scraped from the separatingsurface by a flight conveyor which moves transversely to a dischargedirection of the discharged liquid.
 17. A method according to claim 16,wherein said flight conveyor comprises an endless chain carrying asuccession of scraper flights which are drawn across said separatorsurface toward a ferrous chip discharge.
 18. A method according to claim14, wherein said liquid is discharged from a plurality of spaced liquiddischarge nozzles arranged along said first side of said separatingsurface.
 19. A method according to claim 14, further comprisingregulating the discharge velocity of said liquid to maximize theseparation of ferrous and non-ferrous metal particles.
 20. A methodaccording to claim 14, wherein said liquid on said separating surface ismaintained at a depth of at most 3 cm.
 21. A method according to claim20, wherein said liquid on said separating surface is maintained at adepth of at most 2 cm.
 22. A method according to claim 14, wherein saidseparating surface is comprised of stainless steel.
 23. A methodaccording to claim 14, wherein said magnets are sintered strontiumferrite ceramic magnets.
 24. A method according to claim 23, whereinsaid magnets are stainless steel clad on all sides except the sideadjacent said separating surface.
 25. A method according to claim 14,wherein said liquid is discharged at a velocity of from about 2 to about3 meters per second.
 26. A method according to claim 14, wherein saidmagnets exert a magnetic induction of from 1500 to 3000 gauss throughsaid separating surface.
 27. A method according to claim 26, whereinsaid magnets exert a magnetic induction of from 2000 to 2500 gaussthrough said separating surface.